Sustainable development necessitates that reduction of the negative impact that the construction industry has on the environment. Due to this, alternative, environmentally-friendly building materials such as hemp are being sought.
What is Industrial Hemp?
Hemp is a non-fossil, organic product considered to be carbon negative. One of its many beneficial qualities is that it can be cultivated in environments which do not require the use of pesticides, herbicides and fungicides which have been found to have negative environmental implications. As a construction material, the hemp plant has been used for over 10,000 years with approximately 25,000 different industrial uses.
Uses of Industrial Hemp and Comparisons to Traditional Building Materials
Industrial hemp is quite flexible in the fact that it can be used for a variety of purposes within the construction industry and as a whole compares favourably to building materials typically used.
By using thermal insulation materials, there can be a reduction in heating demands, which, in turn, reduces the ecological footprint associated with the operation of the building. The use of plant-derived materials such as sunflower, flax and hemp in thermal insulation boards are becoming increasingly popular, and their thermal insulating and acoustic properties are similar to conventional insulation. However, one of the advantages of using hemp for insulation is its flexibility. For example, after being compressed, the insulation can return to its original shape. This is useful during the assembling process where squeezing the sheets to insert between the structural compartments is inevitable. Furthermore, the shape of hemp insulation sheets remains the same for long periods of time, which means they do not settle and cause cavities to occur in areas where insulation should be present.
The inner core of the hemp plant, also known as the shiv, can be mixed with water, lime, and binder to produce a mixture with similar consistency and usability as concrete. Commonly referred to as ‘Hempcrete’, this natural material boasts highly insulating qualities as well as being lightweight - it weighs approximately one-eighth of the weight of concrete. Further beneficial properties include soundproofing, air moderation and resistance to mould and pests. Its use is recommended for the creation of floors, roofs and non-structural or weight bearing walls.
One of the downfalls with Hempcrete is that it can take a few weeks to cure compared to the few hours required when using concrete. Due to this, there have been developments which have led to the creation of prefabricated hemp-based, timber-frame panels. Compared to Hempcrete, the panels can be used structurally, and some types allow for a manufacture-drying cycle of 24 hours.
One of the significant benefits of using plant derivatives such as industrial hemp in construction is that they can mitigate some of the negative environmental impacts that other construction materials can create. For example, the manufacturing of certain types of cement involves a large quantity of carbon dioxide emissions.
Specifically, hemp as a building material is considered to be environmentally-friendly as it absorbs large quantities of carbon dioxide during its growth period, which is then locked into the material. During its lifetime, the hemp products will continue to absorb more carbon dioxide from the atmosphere and, in turn, increase the strength of the material. It is thought that 1 tonne of hemp shives could absorb 1.8 tonnes of carbon dioxide, and 1m3 of a lime-hemp mixture wall could absorb 110kg of carbon dioxide.
Research has found that the production of concrete contributes to approximately 5% of global carbon dioxide emissions. Therefore, using industrial hemp may help to make the construction industry a lot cleaner.
As well as the agricultural and environmental benefits of using hemp as a building material, there are prospective economic benefits. The growth cycle of hemp is typically quite short, and cultivation involves very little processing, and fallow time is not needed between crops. Additionally, hemp can be produced cheaply and at a fast rate allowing for higher profit margins for farmers.
Job creation could grow massively in countries wanting to mass produce hemp for industrial use and could create an increased demand for retailers and manufacturers, as well as those growing, harvesting, and processing the material.
Despite there being several benefits of using industrial hemp as a building material, one of the major drawbacks relates to water absorption rates. Hemp-based composite materials can often be exposed to humid climates for extended periods of time during their life cycle. As the natural fibres are cellulose-rich and hydrophilic, exposure to additional moisture may result in the development of internal stress fields. This can result in swelling of the fibres and have a knock-on effect on the material’s mechanical and thermal properties.
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